<!DOCTYPE html>
<html>

	<head>
		<meta charset="UTF-8">
		<title></title>
		<script src="jquery-1.11.1.js"></script>
	</head>

	<body>
		<div id="num"> 2 </div>
		<script>
			/*var a = [1, 2, 3, 4];
									var b = [4, 5, 6];
									var c = a.concat(b);
									alert(c)*/

			/*var a = {};
			var index = 1;
			if (a[index] == undefined) {
				a[index] = "2";
			}
			alert(JSON.stringify(a))*/

			/*$.each([0, 1, 2], function(i, n) {
				if (n == 1) {
					return true;
				}
				alert(n)
			});*/

			function fix(v, bit) {
					var vJia = new Number((v * 1) + 1).toFixed(bit);
					var vJian = new Number(vJia - 1).toFixed(bit);
					return vJian;
			}
			
			alert(fix(-$("#num").text(),2))
		</script>
	</body>

</html>